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IP
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...
Organizations can decide to renumber part or all of their IP address
space for a variety of reasons. Overall motivations for renumbering
are discussed in [RFC2071 ...
... remember there different aspects to the problem, depending on the
scope of the renumbering involved. Remember that even an
enterprise-wide renumbering probably will not affect all IP addresses
visible within the enterprise, since some addresses (e.g., Internet
service providers ...
...
Certain new transmission technologies have tended to redefine the
basic notion of an IP subnet. The numbering plan needs to work with
these new ideas. Legacy bridged ...
... renumber, then some of the potential consequences may include (a)
limited (less than Internet-wide) IP connectivity, or (b) extra cost
to offset the overhead associated with the organization's routing
information ...
... address information. Even so, they rarely
are independent of Layer 3 (IP) address structure. Pure Layer 2
...
... Switches are commonly managed by SNMP applications. These network
management applications communicate with managed devices using IP.
Even if the switch does not do IP forwarding ...
... Even if the switch does not do IP forwarding, it will itself need IP
addresses if it is to be managed. Also, if the clients and servers ...
... clients and servers
in the workgroup are managed by SNMP, they will need IP addresses.
The workgroup, therefore, will need to appear as one or more IP
subnets.
...
... SNMP, they will need IP addresses.
The workgroup, therefore, will need to appear as one or more IP
subnets.
Increasingly, internetworking products are not purely Layer 2 ...
... structure and routers, it is worth reviewing what would appear to be
very basic concepts of IP subnets. The traditional view is that a
single subnet is associated with a single physical ...
... to all others. When the set of hosts in a partial mesh is in a
single IP subnet, partial mesh violates the local model of full
connectivity. Even when there is full meshing, a pessimistic but
reasonable operational model must consider that individual VCs ...
... address to the
access server using PPP's IP configuration option [RFC1332prop]. The
server may validate ...
... virtual circuits, switched frame relay, etc.,
present challenges not considered in the original IP design. The
basic IP decision in forwarding a packet is whether the destination ...
... present challenges not considered in the original IP design. The
basic IP decision in forwarding a packet is whether the destination
is local or remote, in relation to the source host ...
... routers. While most readers will have a good intuitive sense of
this, the principles have refined in the current usage of IP.
A router ...
...
A router receives an inbound IP datagram on one of its interfaces,
and examines some number of bits ...
... start at the
leftmost (i.e., most significant) bit position of the IP address.
Those totalPrefix bits may be completely under the control of the
...
... interface that will take
the routed packet to the next hop IP address in the end-to-end route.
...
... routers, consider that many existing configurations may contain
hard-coded IP addresses that may not be necessary, even if
renumbering were not to occur. Part of a router renumbering effort
...
... Wherever possible, servers should be referenced by DNS name rather
than by IP address. If a specific router implementation only
supports explicit address ...
... DHCP/BOOTP). Configurations that
do this are likely to contain hard-coded IP addresses of the
destination hosts or their subnets ...
... traceroute displays
DNS names rather than IP addresses, certain debugging options can be
transparent through the address transition.
...
...
The most common use of dynamic address assignment is to provide IP
addresses to end systems. Dynamic address assignment, however, is
also used to assign IP addresses ...
... IP
addresses to end systems. Dynamic address assignment, however, is
also used to assign IP addresses to router interfaces. An address
assignment server may assign an IP address ...
... IP addresses to router interfaces. An address
assignment server may assign an IP address to a router either in the
usual DHCP ...
... host at a given time is
random within the pool, DHCP can also return a constant IP address
for a specific MAC address. This may be much easier to manage and
...
... DHCP database if either the MAC address or the IP
address changes. One way to reduce such reconfiguration is to use
Locally-Administered Addresses (LAA ...
...
Specifically, it can interfere with the proper operation of any
protocol that carries an IP address as data, since NAT does not
understand passenger fields and is unaware numbers need to change.
...
... TCP and UDP checksums that are in part based on the
IP header. This includes end-to-end encryption schemes
that include the TCP/UDP ...
... prefix length is implied by the
structure of the high-order bits of the IP address (i.e., the "First
Octet Rule").
...
... routing),
and an even more significant number of host IP implementations.
When planning renumbering, network ...
... routing mechanism that does advertise subnets. An
alternative would be to establish an IP-over-IP tunnel through Router
...
... subnets. An
alternative would be to establish an IP-over-IP tunnel through Router
2, and give this a subnet ...
... Modern routers usually support protocol architectures besides IP.
Some of these architectures, notably DECnet ...
...
Some end hosts running protocol stacks other than IP, notably DECnet,
may change their MAC address ...
...
Dynamic protocol mechanisms that to some extent depend on IP
addresses may be affected by router renumbering. These include
mechanisms that assign or resolve addresses ...
... DNS, etc., may cache
IP addresses. When the router is renumbered, these servers may point
to old addresses ...
... SNMP
data, it is a relatively simple task to define a tool to examine IP
addresses in the configuration, identify those beginning with the old
prefix, and substitute the new prefix ...
... routers are
configured with SNMP), and current IP address. We then want to
compare the addresses in this list to the list defined earlier of
...
...
Note that the explicit definition statement, or at leasts its
variables, should be kept. In the real world, static IP address
mappings in hosts may not have been maintained as systematically as
...
...
Configuration commands in this category assign IP addresses to
physical or virtual interfaces ...
... interfaces on a single router. They also include
commands that assign IP-address-related information to the router
"box" itself, and commands which involve the router ...
...
Traditional IP routers do not have unique identifiers, but rather are
treated as collections of IP addresses ...
... IP routers do not have unique identifiers, but rather are
treated as collections of IP addresses associated with their
interfaces. Some protocol mechanisms ...
... router identifiers is using the "highest
IP address" on the router as an identifier for the "box." Many
...
... Typical applications of a global router ID may not require it be a
"real" IP address that is advertised through the routing domain, but
...
... not recommended. Most implementations have a means of declaring a
pseudo-IP address for the router itself as opposed to any of its
ports ...
... router
renumbering. Interface configuration will require an IP address, and
usually a subnet mask or prefix length ...
... interface S0 to Ethernet
interface E0. They forward every packet on e0 to their local S0.
Neither S0 has an IP address. R1 has the router ID 10.1.0.1/16 and
...
... making it difficult to test whether a connectivity problem is due to
S0 or E0. Some management is possible as long as at least one IP
address on the router (e.g., E0) is reachable, since this will permit
SNMP ...
... identifier. This provides an
address to be used for such functions as the IP Route Recording
option, and for providing a next-hop-address ...
... Frame Relay. OSPF,
for example, uses the IP address of numbered interfaces as a unique
identifier for that interface ...
... MAC addresses to
interfaces. In such cases, an IP address may be part of the MAC
address configuration statements and will need to be changed.
...
... addresses will usually be needed for NBMA
and switched media. When renumbering IP addresses, statements that
map the IP address to frame relay ...
... and switched media. When renumbering IP addresses, statements that
map the IP address to frame relay DLCIs, X.121 addresses ...
... address. Local requirements may require a period of parallel
operation, where the old and new IP addresses map to the same medium
address.
...
... addresses. Pools of addresses may be seen in pure
IP environments, or in multiprotocol situations such as Apple MacIP.
...
... forwarding address assignment requests to the appropriate server(s).
If this is the case, there may be hard-coded references to the IP
addresses of these servers, which may need to be changed as part of
renumbering.
...
... routing updates). Filtering rules
may contain source and/or destination IP addresses that will need to
change as part of a renumbering effort.
...
... events are sent preferably should be identified by DNS name. If the
logging server is referenced by IP address, its address may need to
change during renumbering. Care should be taken that critical ...
... for UDP-based services, or simply for IP. In such services, when an
authorized packet leaves the local environment to go into an
...
... unnumbered interfaces and
physical interfaces with IP addresses in multiple subnets, may not be
transparent to OSPF ...
... prefixes are usually associated with IS-IS area definitions. If
IP prefixes change, there may be a corresponding change in area
definitions.
...
... TFTP. Network management scripts may contain hard-
coded references to IP addresses supporting these services. In
general, try to convert script references to IP addresses ...
... IP addresses supporting these services. In
general, try to convert script references to IP addresses to DNS
names.
...
...
Abnormal condition indications can be sent to several places that may
have hard-coded IP addresses, such as SNMP trap servers, syslogd
servers, etc.
...
... Load-generating scripts used for performance testing may contain
hard-coded IP addresses. Look carefully for scripts that contain
executable code for generating ranges of test addresses ...
... ranges of test addresses. Such
scripts may, at first examination, not appear to contain explicit IP
addresses. They may, for example, contain a "seed" address used with
an incrementing loop.
...
... IP and Protocol Encapsulation ...
...
IP packets can be routed to provide connectivity for non-IP
protocols, or for IP traffic with addresses ...
... IP packets can be routed to provide connectivity for non-IP
protocols, or for IP traffic with addresses not consistent with the
active ...
... "passenger" protocol addresses is mapped to a pair of endpoint IP
addresses. Generic Route Encapsulation is a representative means of
...
...
Renumbering of the primary IP environment often does not mean that
passenger protocol addresses need to change. In fact, such protocol
...
... addresses need to change. In fact, such protocol
encapsulation for IP traffic may be a very viable method for handling
legacy systems ...
... legacy systems that cannot easily be renumbered. For this legacy
case, the legacy IP addresses can be tunneled over the renumbered
routing environment.
...
... routing environment.
Also note that IP may be a passenger protocol over non-IP systems
using IPX ...
... Hubbard, K., Kosters, M., Conrad, D., Karrenberg, D., and J. Postel, "INTERNET REGISTRY IP ALLOCATION GUIDELINES", BCP 12, RFC 2050, November 1996. ...
... Egevang,, K., and P. Francis, "The IP Network Address Translator (NAT)", RFC 1631(-> 3022), May 1994. ...